论文标题

量子几何激子漂移速度

Quantum Geometric Exciton Drift Velocity

论文作者

Cao, Jinlyu, Fertig, H. A., Brey, Luis

论文摘要

我们表明,激子的偶极矩是由其本征态的量子几何形状唯一决定的,并证明了其与我们称为量子几何偶极子(QGD)的数量的紧密联系。 QGD自然出现在电场中激子的半经典动力学中,与浆果的曲率不同,导致异常速度的贡献不同。在均匀的电场中,QGD导致的漂移速度类似于即使没有真实磁场,也可以在交叉电场和磁场中对激发子的期望。我们计算了与半经典激子动力学相关的数量,用于在间隙中具有弱层间隧穿和费米能量的双层系统的几个有趣示例,在该缝隙中,激子可以将激子明智地描述为两体问题。这些数量包括激子分散,其QGD和Berry的曲率。对于消失的磁场中的两个间隙格苯层层,如果层相同,我们发现量子几何偶极子消失,但是当层不同时可能非零。我们在存在磁场的情况下进一步分析了示例,使我们能够检查涉及石墨烯的病例,其中通过Landau水平分裂打开了间隙。还考虑了涉及TMD的异质结构。在每种情况下,量子几何偶极子和浆果的曲率都以不同的方式发挥作用。在某些情况下,发现最低的能量激子状态位于有限的动量处,具有玻璃凝结的有趣可能性。我们还发现,QGD用激动剂动量单调增加的情况,表明可以利用量子几何形状从最初结合的激子与电场产生光电流。我们推测在几何形成层受到相同或不同电场的几何形状中的半经典动力学的进一步可能影响。

We show that the dipole moment of an exciton is uniquely determined by the quantum geometry of its eigenstates, and demonstrate its intimate connection with a quantity we call the Quantum Geometric Dipole (QGD). The QGD arises naturally in semiclassical dynamics of an exciton in an electric field, contributing to the anomalous velocity differently from the Berry's curvature. In a uniform electric field QGD results in a drift velocity akin to that expected for excitons in crossed electric and magnetic fields, even in the absence of a real magnetic field. We compute the quantities relevant to semiclassical exciton dynamics for several interesting examples of bilayer systems with weak interlayer tunneling and Fermi energy in a gap, where the exciton may be sensibly described as a two-body problem. These quantities include the exciton dispersion, its QGD, and Berry's curvature. For two gapped-graphene layers in a vanishing magnetic field, we find the Quantum Geometric Dipole vanishes if the layers are identical, but may be non-zero when the layers differ. We further analyze examples in the presence of magnetic fields, allowing us to examine cases involving graphene, in which a gap is opened by Landau level splitting. Heterostructures involving TMDs are also considered. In each case the Quantum Geometric Dipole and Berry's curvatures play out differently. In some cases, the lowest energy exciton state is found to reside at finite momentum, with interesting possibilities for Bose condensation. We also find situations in which the QGD increases monotonically with exciton momentum, suggesting that the quantum geometry can be exploited to produce photocurrents from initially bound excitons with electric fields. We speculate on further possible effects of the semiclassical dynamics in geometries where the constituent layers are subject to the same or different electric fields.

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